The present invention relates to a hot-vulcanisable, pumpable rubber-based adhesive/sealant suitable for bonding metal sheeting in the construction of automobile shells.
The bonding of metal sheeting in the construction of automobile shells has the objective of sealing cavities and suppressing any vibration which occur. The sheeting used is coated with a number of grams of corrosion-protection oils and drawing oils per square meter, and should be able to absorb these oils. In order to simplify processing and to improve oil absorption, the adhesive/sealant is pumped at temperatures of from about 50.degree. to 80.degree. C. and applied to one side of the sheeting to be bonded. The second sheet is then pressed against the first sheet. It should also be ensured here that the second sheet is not applied until the adhesive/sealant applied has cooled and that, nevertheless, good oil absorption and adhesion are achieved. The adhesive/sealant must be stable for a relatively long time at the processing temperatures. Curing should not take place at temperatures below from about 150.degree. to 200.degree. C., as are usual in the baking ovens used in automobile production.
For the above-mentioned purpose, the use of solvent-free, pumpable, rubber-based adhesives/sealant is known, for example in EP-A-0 097 394, where the rubber component comprises a liquid polybutadiene, to which small amounts of solid polybutadiene can be admixed. However, such adhesives/sealants do not achieve the good adhesion required in automobile production. As used herein, the term "pumpable" refers to a composition that may be pumped, by means of conventional pumps for hot-melt substances, at elevated temperatures such as about 60.degree. C.
EP-A-0 256 316 describes adhesives/sealants having a rubber component comprising polybutadiene liquid rubber and chemically depolymerised solid rubber. The depolymerisation of the solid rubber is said to give better rheological properties. On the other hand, depolymerisation of the solid rubber has the disadvantage of an additional process step.
DE-A-38 34 818 describes an adhesive/sealant whose rubber component comprises polybutadiene liquid rubber containing terminal hydroxyl groups and cis-1,4-polybutadiene solid rubber.
DE-A 27 58 222 discloses pressure-sensitive adhesives for self-adhesive tapes containing tackifying resins, for example polyterpenes or polybutene, and a maleic anhydride-modified liquid polybutadiene. Curing is carried out at room temperature by means of polyamines or poly-epoxides.
Finally, EP-A 0 181 441 discloses cold-curing sealants/adhesives which contain, as binders, hydroxyl-containing homopolymers or copolymers of 1,3-butadiene which carry lateral succinic anhydride groups. Curing is carried out using organic nitrogen bases selected from amines and N-alkylimidazoles.